While the investigation into the origin and cause of the West Fertilizer Plant fire and explosion in West, Texas, is ongoing, investigators say that ammonium nitrate was detonated in the explosion. However, they don’t know how the explosion was initiated.

The Texas State Fire Marshal’s Office originally said the investigation would possibly be completed by May 10. It now says it may take as much as an additional two weeks.

Over 70 investigators from agencies including the State Fire Marshal’s Office and ATF are investigating, according to information released by the Texas Department of Insurance.

The fertilizer facility in West exploded April 17, killing 14 people, injuring more than 200 others and causing an estimated $100 million in damage to the surrounding area.

In emailed message, Texas Insurance Commissioner Eleanor Kitzman said her department “does not have actual knowledge of the existence of or details regarding any liability insurance coverage. While we do not have actual knowledge of or details regarding the insurance coverage, others have estimated that the damages at $100 million, far more than the amount of insurance we have heard the company may have had.”

Lawsuits have been filed West Fertilizer’s owners, Adair Grain, by victims and their families, as well as by insurance companies that covered the many area homes and buildings that were damaged or destroyed by the explosion.

More than 200 leads have developed, investigators say, and more than 400 interviews have been conducted.

Investigators do know the origin of the fire was in the fertilizer and seed building. The investigators continue to work on pinpointing an exact location of the fire’s origin within the building that is over 12,000 square feet.

The cause of the fire that happened prior to the deadly explosion is still unknown..

Investigators have eliminated the following causes for the initial fire: weather, natural causes, anhydrous ammonium, the rail car containing ammonium nitrate, and a fire within the ammonium nitrate bin. The aforementioned items were not the cause of the fire that happened prior to the explosion at the West Fertilizer and Adair Grain facility.

Additionally, water used during firefighting activities did not contribute to the cause of the explosion. The investigation into the deaths of the first responders also continues and is not complete.